Points taken Codex, but a few things to bear in mind
1) Grenades, in the right hands, are far deadlier as spikes than spore mines (that's not to underplay the power of spore mines)
2) Grenades cost energy, spore mines cost 100/5 and 1 pop per mine, possibly with 35 red for the tower. So you have to make up that value in casualties for it to be worth it. It is likely you will get one, maybe 2 detonations on retreat. And you can't expect the mines to survive long after to get more value out of them.
Codex wrote:Compared to a retreat nade or Autarch call in, it's trivial to carry out but equally effective. It's like having an Autarch call in that automatically gives you a template for how to drop your nades in a retreat path. Except that it doesn't cost 150 red.
Sorry mate but not really..yes it is annoying when mines go off in the retreat path like this but tbh most of the time the nid player is actually paying more, just the other guy feels more pissed